Add new language support

Send a pull request to add support for this new language stack to grounds-images.

You may skip this step if grounds-images already supports this language or if a pull request already exist for the same purpose.
Assign a label to your language code in config/editor.yml:

e.g. For PHP:
```
 php: 'PHP'
```
Add to app/assets/javascripts/grounds/utils.js an hello world example:

e.g. For PHP:
```
 utils.samples['php'] = { mode: 'php', code: [
 '<?php',
 '',
 'print("Hello world\\n");'
 ]};
```
N.B. mode may differ from the language code and correspond to Ace mode. You can find a list of Ace modes here.
Require Ace mode from vendor/assets/javascripts:

e.g. For PHP:
```
 //= require ace/mode-php
```
Run the full test suite
```
 make test
```
Send a pull request and mark it blocked by your grounds-images pull request.

If grounds-images already supports this language, don't mark it. If a pull request already exists to add support for this language to grounds-images, mark yours blocked by it.

Thanks for your contribution!

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